Motor fuels



United States Patent a 3,006,741 EC Patented Oct. 31, 1961 3,006,741 MOTOR FUELS Frederick K. Kawahara, Park Forest, 11L, assignor to Standard Oil Company, Chicago, 111., a corporation of Indiana No Drawing. Filed Mar. 31, 1958, Ser. No. 724,930 12 Claims. (Cl. 44-66) severe when petroleum produetsarederiveipr substituents which are derived, from the thermal cracking of high boiling petroleum hydrocarbons. Olefinic materials, in particular diolefins and higher polyolefins, are associated with gum formation and are invariably found in commercial motor fuels which contain blends of thermally cracked gasoline. When motor fuels are to be maintained in storage for any considerable period, it is the practice to incorporate in such fuels an additive to inhibit gum formation.

An object of the present invention is to provide light hydrocarbon distillate fuels resistant to oxidative gum formation. Another object of the invention is to provide I oxidation-stable hydrocarbon motor fuels which are derived at least in part from the thermal cracking of petroleum hydrocarbons. Still another object of the invention is to provide hydrocarbon motor fuels which are made resistant to oxidative gum formation by the incorporation of conventional oxidation inhibitors and a new synergist therefor. Other and more particular objects and advantages of the invention will become apparent from the following description.

In accordance with the objects above it has now been discovered that light hydrocarbon distillate fuels, particularly motor fuels and more particularly those distillates derived from thermal cracking of petroleum hydro- 2 butyl-para-phenylene diamine is an exceptionally effective inhibitor and is commercially available under the trademarks du Pont No. 22 and UOP No. 5.

The perfluoroalkyl-amido-tertiary-amines which have 5 been found to possess an extraordinary synergism in the presence of para-phenylene diamines have been described in such publications as Blake et al., Perfluoroalkyl Surface Active Agents for Hydrocarbon Systems, presented before the Division of Petroleum Chemistry, American Chemical Society, New York Meeting, September 11,

1954. The paper was published by the American Chemical Society in a booklet, Genera-l Papers No. '32, September 1l-17, 1954. The perfiuoroalkyl-amido-tertiary-amines may be prepared by reacting the corresponding perfluoroalkyl carboxylic acid with the corresponding N,N-dialkyl-alkylene diamine; in'turn the per-fluoroalkyl carboxylic acids are obtained by the electrochemical fluorination' of aliphatic carboxylic acids in anhydrous hydrofluoric acid according to the procedure of Kau'ck et al., Ind. Eng. Chem., vol. 43, No. 10, pp. 23-32, October Perfluoroalkyl-amido-tertiary=amines alone have no de tectable inhibiting effect on oxidative gum formation, but require that the phenylene diamine be conjointly present.

25 To illustrate the surprising synergistic eifect of perfluoroalkyl-amido-tertiary-amines on para-phenylene diamine inhibitors, two series of runs were conducted. In the first series, a thermally cracked heavy naphtha was employed as the oxidation-unstable hydrocarbon distillate base stock, and a para-phenylene diamine inhibitor and a perfluoroalkyl-amido-tertiary-amine synergist were incorporated therein, first independently and then in combination. As a measure of the tendency toward gum formation, the respective samples were exposed to the test conditions of ASTM 873-49 for four hours, and the possess the synergistic properties of the tertiary amines claimed.

Example I An unstabilized thermal heavy naphtha was tested according to the above procedure. At the end of four hours it formed 83.5 milligrams of insoluble gum.

carbons, which are normally 'susceptibietomrcidativegunf if formation, may be stabilized by incorporating therein a small but suflicient amount of a conventional paraphenylene diamine inhibitor and a perfiuoroalkyl-amidotertiary-amine synergist. Both the inhibitor and synergist are employed in amounts from about 0.001% to about 1.0%, and preferably from 0.001 percent to 0.01 percent by weight. The perfiuoroalkyl amido tertiary amines suitable for the present purpose have the general structural formula Example II A sample of the above naphtha was inhibited with 0 0.0027% by weight of du Pont'No. 22, or N,,N'-di-secbutyl-para-phenylene diamine, without the perfiuoro alkyl-an'iido-tertiary-amine. In four hours it formed 31.4 milligrams of gum, or a reduction of only 62.5 percent.

Example Ill The thermal naphtha and 0.0027% of perfluorohept'yl- CONH-propylene-N-dirnethyl, without any para-phenylene diamine inhibitor, was tested. The gum formed was 92.9 milligrams, or an actual increase of 10% above Example I where the naphthas contained no additives.

Example IV In accordance with the invention, the thermal naphtha was inhibited with 0.0027% of du Pont No. 22 (N,N'-

di-sec butyl-para-phenylene diamine) and 0.0027% of perfluoroheptyl-CONH-propy1ene-dimethyl. At the end of the four hour test period the sample had deposited oniytii miiiigr amsif gumI This is (Ely 7.5 of the gum deposited by the untreated naphtha in Example -I and is less gum than formed by inhibition with a para-phenylene diamine inhibitor alone. In other words,

the phenylene diamine is rendered five times more effective, or, in the presence of the synergist, only one-fifth the amount of para-phenylene diamine inhibitor need be employed to attain the same degree of oxidation stability.

Examples V and VI To compare perfiuoroalkyl-amido-tertiary-amines with perfiuoroalkyl-amido-tetraalkyl ammonium halides, the compound perfluoroheptyl-CONH propylene-N(CH I was tested both alone and in combination with a paraphenylene diamine. At the 0.0027% concentration level, the perfiuoroalkyl-amido-tetraalkyl ammonium halide alone gave 120.8 milligrams of gum, or approximately 45% more than the thermal naphtha without any additives. The halide, rather than being a synergist for paraphenylene diamine proved antagonistic, and a naphtha containing 0.0027% each of the iodide and du Pont No. 22 deposited 151.2 milligrams of gum.

Examples VII and VIII The compound perfluoroheptyl-CONH-propylene-N- (CH C H Br (referred to as the bromide) when used alone with thermal naphtha greatly promoted gum formation, there being deposited 449.0 milligrams at the end of four hours at the 0.0027% concentration level. As a synergist for N,N-di-sec-butyl-para-phenylene diamine (du Pont No. 22, both at 0.0027% concentration) it was somewhat better than the iodide of Examples V and VI. In four hours, 66.8 milligrams of gum were deposited, or about 11 times the amount of gum that was formed in using the combination of the instant invention (Example IV).

In a second series of eight additional tests the surprising promotional effect of perfluoroalkyl-amido-tertiary-amines on para-phenylene diarnines were further studied. The base stock in each case was a synthetic mixture consisting of 2.5 parts by volume of 2,3-dimethyl butadiene-1,3 in 100 parts of normal heptane. Dimethyl butadiene was selected as it typically represents unstable diolefinic hydrocarbons present in thermally cracked petroleum fractions, and its susceptibility to oxidative gum formation renders it an excellent test stock for quantitative as Well as qualitative comparisons of additives. In each run the amount of the additive employed was 0.0027 by weight.

Examples IX and X The synthetic stock described above, in the absence of any additive, was studied under the conditions of the ASTM 873-49 gum determination test. At the end of four hours, 631.0 and 635.7 milligrams of gum were formed.

Examples XI and XII Examples XIII and XIV A sample of the dimethyl butadiene-normal heptane mixture was inhibited with the commercial phenylene diamine, N,N'-di-sec-butyl-para-phenylene diarnine (du Pont 'No. 22), in the amount of 0.0027%. In two tests of four hours each, 23.6 milligrams of gum was formed in each case.

Examples XV and XVI A mixture of the dimethyl butadiene normal heptane hydrocarbon with commercial N,N'-di-sec-butyl-paraphenylene diamine together with the synergist perfluoro- 4 heptyl-CONH-propylene-N-dimethyl was tested by the standard ASTM method. In four hours only 7.5 milligrams and 13.5 milligrams of gum were for-med, for an average of 10.5 milligramsor a 56.7% reduction of the amount formed with anti-oxidant alone.

In similar manner other perfluoroalkyl-amido-tertiaryamines may be used, and these include for example perfiuoro-N-butyl-CONH-ethylene-N-methyl-ethyl, perfluoroisooctyl-CONH-isobutylene-N-diethyl, perfluorononyl- CONH-hexylene-N-dibutyl, and perfluorododecyl-CONH- propylene-N-dimethyl.

The data in the above sixteen runs demonstrate that the combination of para-phenylene diamine anti-oxidant with perfluoroalkyl-amide-tertiary-amines is vastly superior to the anti-oxidant itself in inhibiting oxidative degradation or gum formation of petroleum distillates. 'Ihe thermally cracked naphtha and the synthetic dimethyl butadiene heptane mixtures tested are representative of the most unstable petroleum hydrocarbons and the data clearly illustrate the advantages obtainable with the combination according to the invention.

Because the perfluoroalkyl-amido-tertiary-amines are sparsely soluble in hydrocarbons, special methods are employed to incorporate the synergists into the distillate stock. The synergist may be mixed with a lower alkanol such as normal propyl alcohol or normal butanol and the resulting solution added to the hydrocarbon; n-butanol method was employed in the examples above. Alternatively, the perfluoroalkyl-amido-tertiary-amine may be dissolved or dispersed in water, the aqueous solution admixed with the hydrocarbon, and the mixture heated to drive off the water. This latter method is very advantageously employed prior to a distillation step in the production of the petroleum stock. Since light petroleum distillates are conveniently produced by thermal or catalytic cracking or by special conversion processes such as reforming, catalytic alkylation, or polymerization, all of which include a final stabilization step, and aqueous mixture of perfluoroalkyl-amido-tertiary-amine synergist, with or without the inhibitor, is advantageously incorporated into the stock before stabilization, and the water removed along with the light ends. The light distillates have an initial boiling point of about F. to about 200 F., those in the gasoline or motor fuel range boil from about to 400 F., and those in the diesel fuel and heating oil range boil from about 350 F. to about 700 F., more or less.

Aside from their herein demonstrated synergistic effects in promoting phenylene diamine inhibitors, perfluoroalkylamido-tertiary-amines are known to have another advantageous property with respect to petroleum distillates. It is reported in the Blake et al. publication previously noted that perfluoroalkyl-amido-tertiary-amines in a concentration of about 0.001 percent or more based on hydrocarbon reduce the surface tension of the mixture by about 50%, thus making for improved efliciency in distillation of hydrocarbons containing these materials. Moreover, and of special commercial significance, perfluoroalkyl-amido-tertiary amines are highly surface active; a few thousands of a percent of these compounds in hydrocarbons is capable of reducing the rate of hydrocarbon evaporation by 75 to 85%. This is especially advantageous when one considers that the usual evaporation loss of volatile petroleum distillates such as motor fuels both during storage and in filling the consumers gasoline tank may amount to several Volume percent. Thus, in addition to improving oxidation resistance, or in providing identical oxidation resistance at greatly reduced phenylene diamine concentrations, the perfiuoroalkyl-amido-tertiaryamines give the added benefits of facilitating distillation and of reducing evaporation loss. Where evaporation loss is considered a major problem, the perfluoroalkyl portion of the synergist is preferably highly branched, rather than straight chain, so as to provide a large molecular volume, and such branching may conveniently be attained by employing perfiuoroalkyl carboxylic acids derived from alco hols produced by the well known x0 reaction.

The perfluoroalkyl-amido-tertiary-amine and para-phenalkyl ylene diamine mixture of the present invention can be I used in combination with conventional petroleum addiperfluomalkyl eONH aJkylen& N tives such as tetraethyllead, alkyl halide scavengers, anga yl a agents, agallts fOf inhibiting Spark P fouling, in which the perfluoroalkyl group contains from 4 to T051011 inhibitors, 12 carbon atoms, the alkylene group contains from 1 Percentages given herein and used in the pp to '6 carbon atoms, and the N-alkyl substituents contain claims are by Weight unless otherwise stated. 1 f 1 to 5 carbon atoms While the invention has been described and illustrated The hydrocarbon motor f l f claim 5 in which by way of preferred embodiments thereof, it will be apthe fl lk l id t ti ry j is -fluo parent to those skilled in the art that variations and modiheptyhCONH PrOpy1en N dh1-1ethy1 fications may bemadewithout departing from the scope h h d f tabilizing a hydrocarbon light disof Present mvwtlon as defined by the appended l5 tillate normally susceptible to oxidative gum formation clams; which comprises incorporating therein from about I dam: r 11 0.001 to 1.0% of a para-phenylene diamine inhibitor i' 'fi fi? eelected from the group consisting of paraphenylen disusceptible to oxidative gum formation, containing in amine N secbuty1 pam pheny1ene diamine, NN'hhseo combination from about 0.001% to 1.0% of a para-phen- 2o butylqparwphenylene diamine, N t butyl pam phenylene ylene diamine inhibitor selected from the group consisting i i N.he y1-para,-pheny1ene diamine and N-d of para-phenylene diamine, N-secbutyl-paraqphenylene di- .decyl para phenylene diamine and from about 001% amine, N,N-di-secbutyl-para-phenylene diamine, N-t-buto of a perfluoroalkyl amide tertiary amine tyl-para-phenylene diamine, N-heXyl-%aphenylene i= gene'fai Structure a amine and N-dodecyl-para-phenylene diamine and from about 0.001 to 1.0% of a perfiuoroalkyl-amido-tertiary- /a1ky1 amine synergist having the general structure perfiuoroalkylc 0NHH1kY1e11eN alkyl alky] in which the perfiuoroalkyl group contains from 4 to 12 pe fl Y O carbon atoms, the alkylene group contains from 1 to 6 my] carbon atoms, and the N-alkyl substituents contain from 1 to 6 carbon atoms. in Which the perfluoroalkyl group contains from 4 to 12 The d of claim 7 in which the perfiuoroalkylcarbon atoms, the alkylene group contains from 1 to 6 amldo'tertlary'amme 1s perfluomheptyl'com'pmpyl" carbon atoms and the N-alkyl substituents contain from 1 to 6 carbon atoms.

2. The stabilized hydrocarbon light distillate of claim 1 in which the perfluoroalkyl-amido-tertiary-amine is perfluoroheptyl-CONH-propyleneaN-dmethyhi m i,

3. A stabilized petroleum hydrocarbon motor fuel obtained at least in part by thermal cracking of petroleum hydrocarbons, and normally susceptibie tomxidative gunr formation, containing in combination from about 0.001% to 1.0% of a para-phenylene diamine inhibitor selected from the group consisting of para-phenylene diamine, N- secbutyl-para-phenylene diamine, N,N'-di-secbutyl-paraphenylene diamine, N-t-butyl-para-phenylene diamine, N-hexyl-para-phenylene diamine and N-dodecyl-paraphenylene diamine and from about 0.001% to 1.0% of a perfluoroalkyl-amido-tertiary-amine synergist having the general structure /alkyl perfluoroalkyl- 0 ON H-alkylene-N alkyl in which the perfluoroalkyl group contains from 4 to 12 carbon atoms, the alkylene group contains from 1 to 6 carbon atoms and the N-alkyl substituents contain from 1 to 6 carbon atoms.

4. The stabilized hydrocarbon motor fuel of claim 3 in which the perfluoroalkyl-amido-tertiary-amine is perfluoroheptyl-CONH-propylene-N-dimethyl.

5. A stabilized hydrocarbon motor fuel of the gasoline boiling range, adapted for spark-ignition internal combustion engines and derived at least in part by thermal cracking of petroleum hydrocarbons, containing from about 0.001% to about 1.0% of a para-phenylene diamine oxidation inhibitor selected from the group conm 12;==A etabiiized hydrecarben meter fuei ei" the gassisting of para-phenylene diamine, N-secbutyl-para-phenylene diamine, N,N-'di-secbutylparaphenylene diamine, N-t-butyLpara-phenylene diamine, N-hexyl' para-phenylene diamine and N-dodecyl-para-phenylene diamine and from about 0.001% to about 1.0% of a perfluoroalikyl- 6 amido-tertiary-amine synergist having the general structure ene-N-dimethyl.

9. A stabilized hydrocarbon light distillate normally susceptible to oxidative gum formation, containing in combination from about 0.001% to 1.0% N,N'-di-secbutyl-para-pheylene diamine and from 0.001% to 1.0% of a perfluoroalkyl-amido-tertiary amine having the general formula alkyl in which the perfluoroalkyl group contains from 4 to 12 carbon atoms, the alkylene group contains from 1 to 6 carbon atoms and the N-a-lkyl substituents contain from 1 to '6 carbon atoms.

10. The stabilized hydrocarbon light distillate of claim 9 in which the perfluoroalkyl-amido-tert-iary amine is perfluoroheptyl-CONH propy1ene-N-dimethyl.

11. A stabilized petroleum hydrocarbon motor fuel obtained at least in part by thermal cracking of petroleum hydrocarbons, and normally susceptible to oxidative gum formation, containing in combination from about 0.001% to 1.0% of an N,N-di-secbutyl-para-phenylene diamine and from about 0.001% to 1.0% of a perfluoroalkylamido-tertiary-amine synergist having the general structure in which the perfluoroalkyl group contains from 4 to 12 carbon atoms, the alkylene group contains from 1 to 6 carbon atoms and the N-alkyl substituents contain from 1 to 6 carbon atoms.

oline boiling range, adapted for spark-ignition internal combustion engines and derived at least in part by thermal cracking of petroleum hydrocarbons, containing from about 0.001% to about 1.0% of N,N- di-secbutylpara-phenylene diamine and from about 0.001% to in which the perfiuoroalkyl group contains from 4 to 12 carbon atoms, the alkylene group contains from 1 to 6 carbon atoms, and the N-alkyl substituents contain from 1 to 6 carbon atoms. 0

References Cited in the file of this patent UNITED STATES PATENTS Little June 8, 1954 Chenicek Jan. 25, 1955 Biswell Feb. 14, 1956 Ahlbrecht Sept. 25, 1956 Barnhart et a1. Feb. 25, 1958 

1. A STABILIZED HYDROCARBON LIGHT DISTILLATE NORMALLY SUSCEPTIBLE TO OXIDATIVE GUM FORMATION, CONTAINING IN COMBINATION FROM ABOUT 0.001% TO 1.0% OF A PARA-PHENYLENE DIAMINE INHIBITOR SELECTED FROM THE GROUP CONSISTING OF PARA-PHENYLENE DIAMINE, N-SECBUTYL-PARA-PHENYLENE DIAMINE, N,N''-DI-SECBUTYL-PARA-PHENYLENE DIAMINE, N-T-BUTYL-PARA-PHENYLENE DIAMINE, N-HEXY-PARA-PHENYLENE DIAMINE AND N-DODECYL-PARA-PHENYLENE DIAMINE AND FROM ABOUT 0.001 TO 1.0% OF A PERFLUOROALKYL-AMIDO-TERTIARYAMINE SYNERGIST HAVING THE GENERAL STRUCTURE 